Functional interactions between herpes simplex virus immediate-early proteins during infection: gene expression as a consequence of ICP27 and different domains of ICP4

Aberrant RNA polymerase initiation and processivity on the genome of a herpes simplex virus 1 mutant lacking ICP27

Within the first 15 minutes of infection, herpes simplex virus 1 immediate early proteins repurpose cellular RNA polymerase (Pol II) for viral transcription. An important role of the viral-infected cell protein 27 (ICP27) is to facilitate viral pre-mRNA processing and export viral mRNA to the cytoplasm. Here, we use precision nuclear run-on followed by deep sequencing (PRO-seq) to characterize transcription of a viral ICP27 null mutant. At 1.5 and 3 hours post infection (hpi), we observed increased total levels of Pol II on the mutant viral genome and accumulation of Pol II downstream of poly A sites indicating increased levels of initiation and processivity. By 6 hpi, Pol II accumulation on specific mutant viral genes was higher than that on wild-type virus either at or upstream of poly A signals, depending on the gene. The PRO-seq profile of the ICP27 mutant on late genes at 6 hpi was similar but not identical to that caused by treatment with flavopiridol, a known inhibitor of RNA processivity. This pattern was different from PRO-seq profiles of other α gene mutants and upon inhibition of viral DNA replication with PAA. Together, these results indicate that ICP27 contributes to the repression of aberrant viral transcription at 1.5 and 3 hpi by inhibiting initiation and decreasing RNA processivity. However, ICP27 is needed to enhance processivity on most late genes by 6 hpi in a mechanism distinguishable from its role in viral DNA replication.IMPORTANCEWe developed and validated the use of a processivity index for precision nuclear run-on followed by deep sequencing data. The processivity index calculations confirm infected cell protein 27 (ICP27) induces downstream of transcription termination on certain host genes. The processivity indices and whole gene probe data implicate ICP27 in transient immediate early gene-mediated repression, a process that also requires ICP4, ICP22, and ICP0. The data indicate that ICP27 directly or indirectly regulates RNA polymerase (Pol II) initiation and processivity on specific genes at specific times post infection. These observations support specific and varied roles for ICP27 in regulating Pol II activity on viral genes in addition to its known roles in post transcriptional mRNA processing and export.

Multi-phenotype analysis for enhanced classification of 11 herpes simplex virus 1 strains

Herpes simplex virus 1 (HSV1) is best known for causing oral lesions and mild clinical symptoms, but it can produce a significant range of disease severities and rates of reactivation. To better understand this phenotypic variation, we characterized 11 HSV1 strains that were isolated from individuals with diverse infection outcomes. We provide new data on genomic and in vitro plaque phenotype analysis for these isolates and compare these data to previously reported quantitation of the disease phenotype of each strain in a murine animal model. We show that integration of these three types of data permitted clustering of these HSV1 strains into four groups that were not distinguishable by any single dataset alone, highlighting the benefits of combinatorial multi-parameter phenotyping. Two strains (group 1) produced a partially or largely syncytial plaque phenotype and attenuated disease phenotypes in mice. Three strains of intermediate plaque size, causing severe disease in mice, were genetically clustered to a second group (group 2). Six strains with the smallest average plaque sizes were separated into two subgroups (groups 3 and 4) based on their different genetic clustering and disease severity in mice. Comparative genomics and network graph analysis suggested a separation of HSV1 isolates with attenuated vs. virulent phenotypes. These observations imply that virulence phenotypes of these strains may be traceable to genetic variation within the HSV1 population.

Manipulation of RNA polymerase III by Herpes Simplex Virus-1

RNA polymerase III (Pol III) transcribes noncoding RNA, including transfer RNA (tRNA), and is commonly targeted during cancer and viral infection. We find that Herpes Simplex Virus-1 (HSV-1) stimulates tRNA expression 10-fold. Perturbation of host tRNA synthesis requires nuclear viral entry, but not synthesis of specific viral transcripts. tRNA with a specific codon bias were not targeted—rather increased transcription was observed from euchromatic, actively transcribed loci. tRNA upregulation is linked to unique crosstalk between the Pol II and III transcriptional machinery. While viral infection results in depletion of Pol II on host mRNA promoters, we find that Pol II binding to tRNA loci increases. Finally, we report Pol III and associated factors bind the viral genome, which suggests a previously unrecognized role in HSV-1 gene expression. These findings provide insight into mechanisms by which HSV-1 alters the host nuclear environment, shifting key processes in favor of the pathogen.

RNA Polymerase III (Pol III) transcribes non-coding RNA, including tRNAs. Applying different RNA-Seq techniques, Dremel et al. provide the Pol III transcriptional landscape of Herpes simplex virus 1 (HSV-1) infected cells. Infection leads to an increase in tRNA expression from host euchromatin and Pol II re-localization to tRNA loci. They also find that Pol III – associated factors bind to the viral genome.

Virus-mediated inactivation of anti-apoptotic Bcl-2 family members promotes Gasdermin-E-dependent pyroptosis in barrier epithelial cells

Two sets of innate immune proteins detect pathogens. Pattern recognition receptors (PRRs) bind microbial products, whereas guard proteins detect virulence factor activities by the surveillance of homeostatic processes within cells. While PRRs are well known for their roles in many types of infections, the role of guard proteins in most infectious contexts remains less understood. Here, we demonstrated that inhibition of protein synthesis during viral infection is sensed as a virulence strategy and initiates pyroptosis in human keratinocytes. We identified the BCL-2 family members MCL-1 and BCL-xL as sensors of translation shutdown. Virus- or chemical-induced translation inhibition resulted in MCL-1 depletion and inactivation of BCL-xL, leading to mitochondrial damage, caspase-3-dependent cleavage of gasdermin E, and release of interleukin-1α (IL-1α). Blocking this pathway enhanced virus replication in an organoid model of human skin. Thus, MCL-1 and BCL-xL can act as guard proteins within barrier epithelia and contribute to antiviral defense.

Engineering HSV-1 Vectors for Gene Therapy

Virus vectors have been employed as gene transfer vehicles for various preclinical and clinical gene therapy applications and with the approval of Glybera (Alipogene tiparvovec) as the first gene therapy product as a standard medical treatment (Yla-Herttuala, Mol Ther 20:1831-1832, 2013), gene therapy has reached the status of being a part of standard patient care. Replication-competent herpes simplex virus (HSV) vectors that replicate specifically in actively dividing tumor cells have been used in Phase I-III human trials in patients with glioblastoma multiforme (GBM), a fatal form of brain cancer, and in malignant melanoma. In fact, Imlygic^® (T-VEC, Talimogene laherparepvec, formerly known as OncoVex GM-CSF), displayed efficacy in a recent Phase-III trial when compared to standard GM-CSF treatment alone (Andtbacka et al., J Clin Oncol 31:sLBA9008, 2013), and has since become the first FDA-approved viral gene therapy product used in standard patient care (October 2015) (Pol et al., Oncoimmunology 5:e1115641, 2016). Moreover, increased efficacy was observed when Imlygic^® was combined with checkpoint inhibitory antibodies as a frontline therapy for malignant melanoma (Ribas et al., Cell 170:1109-1119.e1110, 2017; Dummer et al., Cancer Immunol Immunother 66:683-695, 2017). In addition to the replication-competent oncolytic HSV vectors like T-VEC, replication-defective HSV vectors have been employed in Phase I-II human trials and have been explored as delivery vehicles for disorders such as pain, neuropathy and other neurodegenerative conditions. Research during the last decade on the development of HSV vectors has resulted in the engineering of recombinant vectors that are completely replication defective, nontoxic, and capable of long-term transgene expression in neurons. This chapter describes methods for the construction of recombinant genomic HSV vectors based on the HSV-1 replication-defective vector backbones, steps in their purification, and their small-scale production for use in cell culture experiments as well as preclinical animal studies.

Hidden regulation of herpes simplex virus 1 pre-mRNA splicing and polyadenylation by virally encoded immediate early gene ICP27

In contrast to human cells, very few HSV-1 genes are known to be spliced, although the same pre-mRNA processing machinery is shared. Here, through global analysis of splice junctions in cells infected with HSV-1 and an HSV-1 mutant virus with deletion of infectious cell culture protein 27 (ICP27), one of two viral immediate early (IE) genes essential for viral replication, we identify hundreds of novel alternative splice junctions mapping to both previously known HSV-1 spliced genes and previously unknown spliced genes, the majority of which alter the coding potential of viral genes. Quantitative and qualitative splicing efficiency analysis of these novel alternatively spliced genes based on RNA-Seq and RT-PCR reveals that splicing at these novel splice sites is efficient only when ICP27 is absent; while in wildtype HSV-1 infected cells, the splicing of these novel splice junctions is largely silenced in a gene/sequence specific manner, suggesting that ICP27 not only promotes accumulation of ICP27 targeted transcripts but also ensures correctness of the functional coding sequences through inhibition of alternative splicing. Furthermore, ICP27 toggles expression of ICP34.5, the major viral neurovirulence factor, through inhibition of splicing and activation of a proximal polyadenylation signal (PAS) in the newly identified intron, revealing a novel regulatory mechanism for expression of a viral gene. Thus, through the viral IE protein ICP27, HSV-1 co-opts both splicing and polyadenylation machinery to achieve optimal viral gene expression during lytic infection. On the other hand, during latent infection when ICP27 is absent, HSV-1 likely takes advantages of host splicing machinery to restrict expression of randomly activated antigenic viral genes to achieve immune evasion.

Little is known regarding to how HSV, a large DNA virus and known to contain very few spliced genes, escapes host pre-mRNA splicing machinery. Here, by establishing a high throughput splice junction identification platform and quantitative analysis method to assess splicing efficiency based on high throughput data, we find that HSV-1 encodes hundreds of previously unknown alternative splice junctions; however, splicing of these novel spliced genes is largely silenced in wild-type HSV-1 infected cells, explaining why only very few spliced genes have been previously identified in HSV-1. Moreover, ICP27 is required for splicing inhibition and 3’ end formation of ICP34.5, the major viral neurovirulence factor and also the major target of latently expressed viral miRNAs. These findings not only fundamentally change the view of HSV gene structure, but also reveal a mechanism by which HSV employs host splicing and polyadenylation machineries to achieve optimal gene expression during acute infection and may also contribute to immune evasion during latency when ICP27 is not expressed.

Herpes Simplex Virus Vectors for Gene Transfer to the Central Nervous System

Neurodegenerative diseases (NDs) have a profound impact on human health worldwide and their incidence is predicted to increase as the population ages. ND severely limits the quality of life and leads to early death. Aside from treatments that may reduce symptoms, NDs are almost completely without means of therapeutic intervention. The genetic and biochemical basis of many NDs is beginning to emerge although most have complex etiologies for which common themes remain poorly resolved. Largely relying on progress in vector design, gene therapy is gaining increasing support as a strategy for genetic treatment of diseases. Here we describe recent developments in the engineering of highly defective herpes simplex virus (HSV) vectors suitable for transfer and long-term expression of large and/or multiple therapeutic genes in brain neurons in the complete absence of viral gene expression. These advanced vector platforms are safe, non-inflammatory, and persist in the nerve cell nucleus for life. In the near term, it is likely that HSV can be used to treat certain NDs that have a well-defined genetic cause. As further information on disease etiology becomes available, these vectors may take on an expanded role in ND therapies, including gene editing and repair.

Morphological changes in different populations of bladder afferent neurons detected by herpes simplex virus (HSV) vectors with cell-type-specific promoters in mice with spinal cord injury

Functional and morphological changes in C-fiber bladder afferent pathways are reportedly involved in neurogenic detrusor overactivity (NDO) after spinal cord injury (SCI). This study examined the morphological changes in different populations of bladder afferent neurons after SCI using replication-defective herpes simplex virus (HSV) vectors encoding the mCherry reporter driven by neuronal cell-type-specific promoters. Spinal intact (SI) and SCI mice were injected into the bladder wall with HSV mCherry vectors driven by the cytomegalovirus (CMV) promoter, CGRP promoter, TRPV1 promoter or neurofilament 200 (NF200) promoter. Two weeks after vector inoculation into the bladder wall, L1 and L6 dorsal root ganglia (DRG) were removed bilaterally for immunofluorescent staining using anti-mCherry antibody. The number of CMV promoter vector-labeled neurons was not altered after SCI. The number of CGRP and TRPV1 promoter vector-labeled neurons was significantly increased whereas the number of NF200 vector-labeled neurons was decreased in L6 DRG after SCI. The median size of CGRP promoter-labeled C-fiber neurons was increased from 247.0 in SI mice to 271.3μm² in SCI mice whereas the median cell size of TRPV1 promoter vector-labeled neurons was decreased from 245.2 in SI mice to 216.5μm² in SCI mice. CGRP and TRPV1 mRNA levels of laser-captured bladder afferent neurons labeled with Fast Blue were significantly increased in SCI mice compared to SI mice. Thus, using a novel HSV vector-mediated neuronal labeling technique, we found that SCI induces expansion of the CGRP- and TRPV1-expressing C-fiber cell population, which could contribute to C-fiber afferent hyperexcitability and NDO after SCI.

Synergistic effects of deleting multiple nonessential elements in nonreplicative HSV-1 BAC genomic vectors play a critical role in their viability

Nonreplicative Herpes simplex virus type-1 (HSV-1) genomic vectors have already entered into clinical trials for neurological gene therapy thanks to their scalable growth in permissive cells. However, the small transgene capacity of this type of HSV-1 vectors currently used in the clinic represents an important limiting factor as a gene delivery system. To develop high-capacity nonreplicative genomic HSV-1 vectors, in this study we have characterized a series of multiply deleted mutants which we have constructed in bacterial artificial chromosomes (BACs), removing up to 24 kb of unstable or dispensable genomic sequences to allow insertion of transgenes up to this size. We show that synergistic effects of deletions of: the HSV-1 replication origins ori_S and ori_L, the HSV-1 internal repeat region, the remaining ICP4 gene copy and the genes encoding for ICP27, U_L56, U_L55, can severely reduce the growth of these HSV-1 vectors. Given that several of these elements have been characterized as 'non-essential' for viral growth in cell culture by single-deletion experiments of wild-type HSV-1, our study highlights the need to re-evaluate their functional contribution in the context of multiply deleted nonreplicative HSV-1 genomic vectors. Our BAC mutants described here can serve as useful starting platforms to accelerate HSV-1 vector development.

Herpes Simplex Virus and Interferon Signaling Induce Novel Autophagic Clusters in Sensory Neurons

Herpes simplex virus 1 (HSV-1) establishes lifelong infection in the neurons of trigeminal ganglia (TG), cycling between productive infection and latency. Neuronal antiviral responses are driven by type I interferon (IFN) and are crucial to controlling HSV-1 virulence. Autophagy also plays a role in this neuronal antiviral response, but the mechanism remains obscure. In this study, HSV-1 infection of murine TG neurons triggered unusual clusters of autophagosomes, predominantly in neurons lacking detectable HSV-1 antigen. Treatment of neurons with IFN-β induced a similar response, and cluster formation by infection or IFN treatment was dependent upon an intact IFN-signaling pathway. The autophagic clusters were decorated with both ISG15, an essential effecter of the antiviral response, and p62, a selective autophagy receptor. The autophagic clusters were not induced by rapamycin or starvation, consistent with a process of selective autophagy. While clusters were triggered by other neurotropic herpesviruses, infection with unrelated viruses failed to induce this response. Following ocular infection in vivo, clusters formed exclusively in the infected ophthalmic branch of the TG. Taken together, our results show that infection with HSV and antiviral signaling in TG neurons produce an unorthodox autophagic response. This autophagic clustering is associated with antiviral signaling, the presence of viral genome, and the absence of HSV protein expression and may therefore represent an important neuronal response to HSV infection and the establishment of latency.

IMPORTANCE

Herpes simplex virus type 1 (HSV-1) is a ubiquitous virus and a significant cause of morbidity and some mortality. It is the causative agent of benign cold sores, but it can also cause blindness and life-threatening encephalitis. The success of HSV-1 is largely due to its ability to establish lifelong latent infections in neurons and to occasionally reactivate. The exact mechanisms by which neurons defend against virus infection is poorly understood, but such defense is at least partially mediated by autophagy, an intracellular pathway by which pathogens and other unwanted cargoes are degraded. The study demonstrates and investigates a new autophagic structure that appears to be specific to the interaction between neurotropic herpesviruses and murine primary sensory neurons. This work may therefore have important implications for our understanding of latency and reactivation.

In search for effective and definitive treatment of herpes simplex virus type 1 (HSV-1) infections

Herpes Simplex Virus type 1 (HSV-1) is a nuclear replicating enveloped virus.

Synthesis of multi ring-fused imidazo [1,2- a]isoquinoline-based fluorescent scaffold as anti-Herpetic agent

BACKGROUND

Natural product-inspired synthesis is a key incorporation in modern diversity-oriented synthesis to yield biologically novel scaffold. Inspired by β-carboline fused system, we have designed molecules with multi ring fused scaffold by modifying the tricyclic pyrido[3,4- b]indole ring with imidazo[1,2- a]isoquinoline.

METHODS

A highly convergent approach with new C-N and C-C bond formation to synthesize multiring fused complex scaffold imidazo[1,2- a]isoquinolinies as fluorophores. N-nucleophile-induced ring transformation of 2 H-pyran-2-one followed by in situ cis-stilbene-type oxidative photocyclization yielded new C-C bond formation without additional oxidant. The cytotoxicity, effective concentrations, and the mode of action of the synthesized analogs were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT),, plaque reduction, time of addition, and reverse transcriptase Polymerase Chain Reaction (PCR).

RESULTS

Novel imidazo[1,2- a]isoquinoline analogs were prepared, and the results revealed that trans isomer of cyclopropyl analog (EC₅₀ 35 and 37.5 µg/ml) and trans isomer of citric acid salt of phenyl analog (EC₅₀ 38.2 and 39.8 µg/ml) possess significant anti-Herpes Simplex Virus (HSV) activity with selectivity index of >10. The kinetic study demonstrated that both the analogs inhibited HSV-1F and HSV-2G at 2-4 h postinfection. Finally, western blot and reverse transcriptase PCR assays revealed that both the analogs suppressed viral immediate early transcription.

CONCLUSION

Novel imidazo[1,2- a]isoquinoline analogs were synthesized from pyranone with appropriate amines. Two compounds showed better antiviral profile on HSV-infected Vero cells, compared to the standard drug acyclovir (ACV). Overall, we discovered a promising scaffold to develop a nonnucleoside lead targeting the viral immediate early transcription for the management of HSV infections.

Selective recruitment of nuclear factors to productively replicating herpes simplex virus genomes

Much of the HSV-1 life cycle is carried out in the cell nucleus, including the expression, replication, repair, and packaging of viral genomes. Viral proteins, as well as cellular factors, play essential roles in these processes. Isolation of proteins on nascent DNA (iPOND) was developed to label and purify cellular replication forks. We adapted aspects of this method to label viral genomes to both image, and purify replicating HSV-1 genomes for the identification of associated proteins. Many viral and cellular factors were enriched on viral genomes, including factors that mediate DNA replication, repair, chromatin remodeling, transcription, and RNA processing. As infection proceeded, packaging and structural components were enriched to a greater extent. Among the more abundant proteins that copurified with genomes were the viral transcription factor ICP4 and the replication protein ICP8. Furthermore, all seven viral replication proteins were enriched on viral genomes, along with cellular PCNA and topoisomerases, while other cellular replication proteins were not detected. The chromatin-remodeling complexes present on viral genomes included the INO80, SWI/SNF, NURD, and FACT complexes, which may prevent chromatinization of the genome. Consistent with this conclusion, histones were not readily recovered with purified viral genomes, and imaging studies revealed an underrepresentation of histones on viral genomes. RNA polymerase II, the mediator complex, TFIID, TFIIH, and several other transcriptional activators and repressors were also affinity purified with viral DNA. The presence of INO80, NURD, SWI/SNF, mediator, TFIID, and TFIIH components is consistent with previous studies in which these complexes copurified with ICP4. Therefore, ICP4 is likely involved in the recruitment of these key cellular chromatin remodeling and transcription factors to viral genomes. Taken together, iPOND is a valuable method for the study of viral genome dynamics during infection and provides a comprehensive view of how HSV-1 selectively utilizes cellular resources.

The intrinsic disorder alphabet. III. Dual personality of serine

Proteins are natural polypeptides consisting of 20 major amino acid residues, content and order of which in a given amino acid sequence defines the ability of a related protein to fold into unique functional state or to stay intrinsically disordered. Amino acid sequences code for both foldable (ordered) proteins/domains and for intrinsically disordered proteins (IDPs) and IDP regions (IDPRs), but these sequence codes are dramatically different. This difference starts with a very general property of the corresponding amino acid sequences, namely, their compositions. IDPs/IDPRs are enriched in specific disorder-promoting residues, whereas amino acid sequences of ordered proteins/domains typically contain more order-promoting residues. Therefore, the relative abundances of various amino acids in ordered and disordered proteins can be used to scale amino acids according to their disorder promoting potentials. This review continues a series of publications on the roles of different amino acids in defining the phenomenon of protein intrinsic disorder and represents serine, which is the third most disorder-promoting residue. Similar to previous publications, this review represents some physico-chemical properties of serine and the roles of this residue in structures and functions of ordered proteins, describes major posttranslational modifications tailored to serine, and finally gives an overview of roles of serine in structure and functions of intrinsically disordered proteins.

Engineering HSV-1 vectors for gene therapy

Virus vectors have been employed as gene transfer vehicles for various preclinical and clinical gene therapy applications, and with the approval of Glybera (alipogene tiparvovec) as the first gene therapy product as a standard medical treatment (Yla-Herttuala, Mol Ther 20: 1831-1832, 2013), gene therapy has reached the status of being a part of standard patient care. Replication-competent herpes simplex virus (HSV) vectors that replicate specifically in actively dividing tumor cells have been used in Phase I-III human trials in patients with glioblastoma multiforme, a fatal form of brain cancer, and in malignant melanoma. In fact, T-VEC (talimogene laherparepvec, formerly known as OncoVex GM-CSF) displayed efficacy in a recent Phase III trial when compared to standard GM-CSF treatment alone (Andtbacka et al. J Clin Oncol 31: sLBA9008, 2013) and may soon become the second FDA-approved gene therapy product used in standard patient care. In addition to the replication-competent oncolytic HSV vectors like T-VEC, replication-defective HSV vectors have been employed in Phase I-II human trials and have been explored as delivery vehicles for disorders such as pain, neuropathy, and other neurodegenerative conditions. Research during the last decade on the development of HSV vectors has resulted in the engineering of recombinant vectors that are totally replication defective, nontoxic, and capable of long-term transgene expression in neurons. This chapter describes methods for the construction of recombinant genomic HSV vectors based on the HSV-1 replication-defective vector backbones, steps in their purification, and their small-scale production for use in cell culture experiments as well as preclinical animal studies.

Herpes simplex virus type 1 single strand DNA binding protein and helicase/primase complex disable cellular ATR signaling

Herpes Simplex Virus type 1 (HSV-1) has evolved to disable the cellular DNA damage response kinase, ATR. We have previously shown that HSV-1-infected cells are unable to phosphorylate the ATR substrate Chk1, even under conditions in which replication forks are stalled. Here we report that the HSV-1 single stranded DNA binding protein (ICP8), and the helicase/primase complex (UL8/UL5/UL52) form a nuclear complex in transfected cells that is necessary and sufficient to disable ATR signaling. This complex localizes to sites of DNA damage and colocalizes with ATR/ATRIP and RPA, but under these conditions, the Rad9-Rad1-Hus1 checkpoint clamp (9-1-1) do not. ATR is generally activated by substrates that contain ssDNA adjacent to dsDNA, and previous work from our laboratory has shown that ICP8 and helicase/primase also recognize this substrate. We suggest that these four viral proteins prevent ATR activation by binding to the DNA substrate and obstructing loading of the 9-1-1 checkpoint clamp. Exclusion of 9-1-1 prevents recruitment of TopBP1, the ATR kinase activator, and thus effectively disables ATR signaling. These data provide the first example of viral DNA replication proteins obscuring access to a DNA substrate that would normally trigger a DNA damage response and checkpoint signaling. This unusual mechanism used by HSV suggests that it may be possible to inhibit ATR signaling by preventing recruitment of the 9-1-1 clamp and TopBP1.

DNA viruses that replicate in the nucleus have been shown to both activate and inactivate various components of the cellular DNA damage response (DDR). Previous reports from our laboratory and others have demonstrated that Herpes Simplex Virus (HSV) utilizes some aspects of the DDR while inactivating others. Paradoxically, HSV utilizes the DDR kinase ATR to complete its life cycle while at the same time disabling the kinase from activating DDR signaling. In this report we provide detail describing the mechanism of ATR inactivation. ATR is normally activated in response to single strand DNA (ssDNA), which serves as a scaffold to recruit several proteins required for complete ATR activation. In this paper we provide evidence that the HSV encoded ssDNA binding protein and helicase/primase complex function to mask the DNA substrate that recruits the ATR kinase activator. This represents the first example of viral DNA replication proteins masking a DNA substrate that could be sensed by the cell as damaged DNA and activate checkpoint signaling. It also explains how ATR can be recruited to sites of viral DNA replication in the absence of checkpoint signaling.

HSV-1 as a Model for Emerging Gene Delivery Vehicles

The majority of viral vectors currently used possess modest cargo capability (up to 40 kb) being based on retroviruses, lentiviruses, adenoviruses, and adenoassociated viruses. These vectors have made the most rapid transition from laboratory to clinic because their small genomes have simplified their characterization and modification. However, there is now an increasing need both in research and therapy to complement this repertoire with larger capacity vectors able to deliver multiple transgenes or to encode complex regulatory regions, constructs which can easily span more than 100 kb. Herpes Simplex Virus Type I (HSV-1) is a well-characterized human virus which is able to package about 150 kb of DNA, and several vector systems are currently in development for gene transfer applications, particularly in neurons where other systems have low efficiency. However, to reach the same level of versatility and ease of use as that of smaller genome viral vectors, simple systems for high-titer production must be developed. This paper reviews the major HSV-1 vector systems and analyses the common elements which may be most important to manipulate to achieve this goal.

The N terminus and C terminus of herpes simplex virus 1 ICP4 cooperate to activate viral gene expression

Infected cell polypeptide 4 (ICP4) activates transcription from most viral promoters. Two transactivation domains, one N-terminal and one C terminal, are largely responsible for the activation functions of ICP4. A mutant ICP4 molecule lacking the C-terminal activation domain (n208) efficiently activates many early genes, whereas late genes are poorly activated, and virus growth is severely impaired. The regions within the N terminus of ICP4 (amino acids 1 to 210) that contribute to activation were investigated by analysis of deletion mutants in the presence or absence of the C-terminal activation domain. The mutants were assessed for their abilities to support viral replication and to regulate gene expression. Several deletions in regions conserved in other alphaherpesviruses resulted in impaired activation and viral growth, without affecting DNA binding. The single small deletion that had the greatest effect on activation in the absence of the C terminus corresponded to a highly conserved stretch of amino acids between 81 and 96, rendering the molecule nonfunctional. However, when the C terminus was present, the same deletion had a minimal effect on activity. The amino terminus of ICP4 was predicted to be relatively disordered compared to the DNA-binding domain and the C-terminal 500 amino acids. Moreover, the amino terminus appears to be in a relatively extended conformation as determined by the hydrodynamic properties of several mutants. The data support a model where the amino terminus is an extended and possibly flexible region of the protein, allowing it to efficiently interact with multiple transcription factors at a distance from where it is bound to DNA, thereby enabling ICP4 to function as a general activator of polymerase II transcription. The C terminus of ICP4 can compensate for some of the mutations in the N terminus, suggesting that it either specifies redundant interactions or enables the amino terminus to function more efficiently.

Herpes simplex virus requires poly(ADP-ribose) polymerase activity for efficient replication and induces extracellular signal-related kinase-dependent phosphorylation and ICP0-dependent nuclear localization of tankyrase 1

Tankyrase 1 is a poly(ADP-ribose) polymerase (PARP) which localizes to multiple subcellular sites, including telomeres and mitotic centrosomes. Poly(ADP-ribosyl)ation of the nuclear mitotic apparatus (NuMA) protein by tankyrase 1 during mitosis is essential for sister telomere resolution and mitotic spindle pole formation. In interphase cells, tankyrase 1 resides in the cytoplasm, and its role therein is not well understood. In this study, we found that herpes simplex virus (HSV) infection induced extensive modification of tankyrase 1 but not tankyrase 2. This modification was dependent on extracellular signal-regulated kinase (ERK) activity triggered by HSV infection. Following HSV-1 infection, tankyrase 1 was recruited to the nucleus. In the early phase of infection, tankyrase 1 colocalized with ICP0 and thereafter localized within the HSV replication compartment, which was blocked in cells infected with the HSV-1 ICP0-null mutant R7910. In the absence of infection, ICP0 interacted with tankyrase 1 and efficiently promoted its nuclear localization. HSV did not replicate efficiently in cells depleted of both tankyrases 1 and 2. Moreover, XAV939, an inhibitor of tankyrase PARP activity, decreased viral titers to 2 to 5% of control values. We concluded that HSV targets tankyrase 1 in an ICP0- and ERK-dependent manner to facilitate its replication.

The herpes simplex virus-1 transactivator infected cell protein-4 drives VEGF-A dependent neovascularization

Herpes simplex virus-1 (HSV-1) causes lifelong infection affecting between 50 and 90% of the global population. In addition to causing dermal lesions, HSV-1 is a leading cause of blindness resulting from recurrent corneal infection. Corneal disease is characterized by loss of corneal immunologic privilege and extensive neovascularization driven by vascular endothelial growth factor-A (VEGF-A). In the current study, we identify HSV-1 infected cells as the dominant source of VEGF-A during acute infection, and VEGF-A transcription did not require TLR signaling or MAP kinase activation. Rather than being an innate response to the pathogen, VEGF-A transcription was directly activated by the HSV-1 encoded immediate early transcription factor, ICP4. ICP4 bound the proximal human VEGF-A promoter and was sufficient to promote transcription. Transcriptional activation also required cis GC-box elements common to the VEGF-A promoter and HSV-1 early genes. Our results suggest that the neovascularization characteristic of ocular HSV-1 disease is a direct result of HSV-1's major transcriptional regulator, ICP4, and similarities between the VEGF-A promoter and those of HSV-1 early genes.

Herpes simplex virus-type 1 is the leading cause of infectious corneal blindness in the industrialized world. Most of the morbidity associated with the virus is due to the host response to episodic reactivation of latent virus. Corneal immunologic privilege is associated with a number of factors including the absence of blood and lymphatic vessels. Conversely, corneal hem (blood)- and lymph-angiogenesis driven by inflammation correlate with the loss of privilege. Neovascularization is a common phenomenon in HSV-1 keratitis that correlates with poor prognosis. We have previously discovered HSV-1 elicits corneal lymphangiogenesis through a unique mechanism involving vascular endothelial growth factor (VEGF)-A independent of that described for other insults including transplantation or bacterial infection. However, the viral-encoded product(s) that elicit host production of VEGF-A is(are) unknown. In this paper, we have identified infected cell protein-4 (ICP4) as the primary virus-encoded product that drives VEGF-A expression. As VEGF-A is involved in driving neovascularization associated with tumor growth and metastasis, proteins that influence transcriptional regulation of VEGF-A may be useful in the development of adjunct therapy for such disparate diseases as cancer and HSV-1 keratitis.

DNA mismatch repair proteins are required for efficient herpes simplex virus 1 replication

Herpes simplex virus 1 (HSV-1) is a double-stranded DNA virus that replicates in the nucleus of its human host cell and is known to interact with many cellular DNA repair proteins. In this study, we examined the role of cellular mismatch repair (MMR) proteins in the virus life cycle. Both MSH2 and MLH1 are required for efficient replication of HSV-1 in normal human cells and are localized to viral replication compartments. In addition, a previously reported interaction between MSH6 and ICP8 was confirmed by coimmunoprecipitation and extended to show that UL12 is also present in this complex. We also report for the first time that MLH1 associates with ND10 nuclear bodies and that like other ND10 proteins, MLH1 is recruited to the incoming genome. Knockdown of MLH1 inhibits immediate-early viral gene expression. MSH2, on the other hand, which is generally thought to play a role in mismatch repair at a step prior to that of MLH1, is not recruited to incoming genomes and appears to act at a later step in the viral life cycle. Silencing of MSH2 appears to inhibit early gene expression. Thus, both MLH1 and MSH2 are required but appear to participate in distinct events in the virus life cycle. The observation that MLH1 plays an earlier role in HSV-1 infection than does MSH2 is surprising and may indicate a novel function for MLH1 distinct from its known MSH2-dependent role in mismatch repair.

Generation of replication-competent and -defective HSV vectors

INTRODUCTION

Engineering effective vectors has been crucial to the efficient delivery and expression of therapeutic gene products in vivo. Among these, HSV-1 represents an excellent candidate vector for delivery to the peripheral and central nervous systems. The natural biology of HSV-1 includes the establishment of a lifelong latent state in neurons in which the viral genome persists as an episomal molecule. Genomic HSV vectors can be produced that are completely replication-defective, nontoxic, and capable of long-term transgene expression. Herpes simplex virus (HSV) vectors are constructed by using a replication-deficient vector backbone (TOZ.1) for homologous recombination with a shuttle plasmid containing a cassette expressing the gene of interest inserted into the UL41 gene sequence. The TOZ.1 vector expresses a reporter gene (lacZ) in the UL41 locus, such that recombination of the transgenic cassette into the UL41 locus results in the loss of the reporter gene activity. The TOZ.1 vector also contains a unique PacI endonuclease site for digestion of parental viral DNA that substantially reduces the nonrecombinant background. Following homologous recombination of the shuttle plasmid into the PacI-digested TOZ.1 genome, the recombinants are identified as clear plaques. After three rounds of limiting dilution analysis, the structure of the recombinants can be confirmed by Southern blot or by polymerase chain reaction (PCR) analysis.

Herpes simplex virus 1 ICP4 forms complexes with TFIID and mediator in virus-infected cells

The infected cell polypeptide 4 (ICP4) of herpes simplex virus 1 (HSV-1) is a regulator of viral transcription that is required for productive infection. Since viral genes are transcribed by cellular RNA polymerase II (RNA pol II), ICP4 must interact with components of the pol II machinery to regulate viral gene expression. It has been shown previously that ICP4 interacts with TATA box-binding protein (TBP), TFIIB, and the TBP-associated factor 1 (TAF1) in vitro. In this study, ICP4-containing complexes were isolated from infected cells by tandem affinity purification (TAP). Forty-six proteins that copurified with ICP4 were identified by mass spectrometry. Additional copurifying proteins were identified by Western blot analysis. These included 11 components of TFIID and 4 components of the Mediator complex. The significance of the ICP4-Mediator interaction was further investigated using immunofluorescence and chromatin immunoprecipitation. Mediator was found to colocalize with ICP4 starting at early and continuing into late times of infection. In addition, Mediator was recruited to viral promoters in an ICP4-dependent manner. Taken together, the data suggest that ICP4 interacts with components of TFIID and Mediator in the context of viral infection, and this may explain the broad transactivation properties of ICP4.

Gene therapy as future treatment of erectile dysfunction

IMPORTANCE OF THE FIELD

Erectile dysfunction (ED) is a major men's health problem. Although the high success rate of treating ED by phosphodiesterase 5 (PDE5) inhibitors has been reported, there are a significant number of ED patients who do not respond to currently available treatment modalities.

AREAS COVERED IN THIS REVIEW

To elucidate the current status of gene therapy applications for ED, gene therapy approaches for ED treatment are reviewed.

WHAT THE READER WILL GAIN

Gene therapy strategies that can enhance nitric oxide (NO) production or NO-mediated signaling pathways, growth factor-mediated nerve regeneration or K(+) channel activity in the smooth muscle could be promising approaches for the treatment of ED. Although the majority of gene therapy studies are still in the preclinical phase, the first clinical trial using non-viral gene transfer of Ca(2+)-activated, large-conductance K(+) channels into the corpus cavernosum of ED patients showed positive results.

TAKE HOME MESSAGE

Gene therapy represents an exciting future treatment option for ED, especially for people with severe ED unresponsive to current first-line therapies such as PDE5 inhibitors although the long-term safety of both viral and non-viral gene therapies should be established.

ATR and ATRIP are recruited to herpes simplex virus type 1 replication compartments even though ATR signaling is disabled

Although the herpes simplex virus type 1 (HSV-1) genome might be expected to induce a DNA damage response, the ATR kinase is not activated in infected cells. We previously proposed that spatial uncoupling of ATR from its interaction partner, ATRIP, could be the basis for inactivation of the ATR kinase in infected cells; however, we now show that ATR and ATRIP are in fact both recruited to HSV-1 replication compartments and can be coimmunoprecipitated from infected-cell lysates. ATRIP and replication protein A (RPA) are recruited to the earliest detectable prereplicative sites, stage II microfoci. In a normal cellular DNA damage response, ATR/ATRIP are recruited to stretches of RPA-coated single-stranded DNA in an RPA- and kinase-dependent manner, resulting in the phosphorylation of RPA by ATR in damage foci. In contrast, in HSV-1-infected cells, RPA is not phosphorylated, and endogenous phosphorylated RPA is excluded from stage II microfoci; in addition, the recruitment of ATR/ATRIP is independent of RPA and the kinase activity of ATR. Furthermore, we show that ATR/ATRIP play a beneficial role in viral gene expression and virus production. Although ICP0 has been shown to be important for partial inactivation of other cellular DNA repair pathways, we show that ICP0 is not responsible for the inactivation of ATR signaling and, furthermore, that neither ATR nor ATRIP is a target of ICP0 degradation. Thus, ATR and ATRIP may function outside the context of the canonical ATR damage signaling pathway during HSV-1 infection to participate in the viral life cycle.

Emerging gene and stem cell therapies for the treatment of erectile dysfunction

Erectile dysfunction is a prevalent condition that leads to significant morbidity and distress, not just for affected men but also for their partners. Very few currently available treatments ameliorate the underlying causes of the disorder and 'cure' the disease state. Much recent effort has been focused on the development of gene and cell-based approaches to rectify the molecular and tissue defects responsible for ED. Gene therapy has been investigated in animal models as a means to restore normal function to the penis; at this time, however, only one human trial has been published in the peer-reviewed literature. Recent gene therapy studies have focused on the modulation of enzymes associated with the NOS/cGMP pathway, and supplementation of trophic factors, peptides and potassium channels. Stem cell therapy has been a topic of interest in more recent years but there are currently very few published reports in animal models and none in human men. Although stem cell therapy offers the potential for restoration of functional tissues, legitimate concerns remain regarding the long-term fate of stem cells. The long-term safety of both gene and stem cell therapy must be thoroughly investigated before large-scale human studies can be considered.

Herpes Virus Amplicon Vectors

Since its emergence onto the gene therapy scene nearly 25 years ago, the replication-defective Herpes Simplex Virus Type-1 (HSV-1) amplicon has gained significance as a versatile gene transfer platform due to its extensive transgene capacity, widespread cellular tropism, minimal immunogenicity, and its amenability to genetic manipulation. Herein, we detail the recent advances made with respect to the design of the HSV amplicon, its numerous in vitro and in vivo applications, and the current impediments this virus-based gene transfer platform faces as it navigates a challenging path towards future clinical testing.

Inhibition of HSV-1 ocular infection with morpholino oligomers targeting ICP0 and ICP27

Alternative therapies are needed for HSV-1 infections in patients refractory to treatment with Acyclovir (ACV) and its derivatives. Peptide-conjugated phosphorodiamidate morpholino oligomers (PPMO) are single-stranded DNA analogues that enter cells readily and reduce target gene expression through steric blockage of complementary RNA. When applied before or soon after infection PPMO targeting the translation-start-site regions of HSV-1 ICP0 or ICP27 mRNA reduced HSV-1 plaque formation by 70-98% in vitro. The ICP0 PPMO also reduced ACV-resistant HSV-1 (strain 615.9) plaque formation by 70-90%, while an equivalent dose of ACV produced only 40-50% inhibition when the treatment was applied between 1 and 3hpi. Seven daily topical treatments of 100microg ICP0 PPMO caused no gross or microscopic damage to the corneas of uninfected mice. Topical application of 10microg ICP0 PPMO to the eyes of HSV-1 infected mice reduced the incidence of eye disease by 37.5-50% compared to controls. This study demonstrates that topically applied PPMO holds promise as an antiviral drug candidate against HSV-1 ocular infection.

Herpes simplex virus vector-mediated gene delivery of glutamic acid decarboxylase reduces detrusor overactivity in spinal cord-injured rats

We examined whether replication-defective herpes simplex virus (HSV) vectors encoding the 67 kDa form of the glutamic acid decarboxylase (GAD(67)) gene product, the gamma-aminobutyric acid (GABA) synthesis enzyme, can suppress detrusor overactivity (DO) in rats with spinal cord injury (SCI). One week after spinalization, HSV vectors expressing GAD and green fluorescent protein (GFP) (HSV-GAD) were injected into the bladder wall. Rats with SCI without HSV injection (HSV-untreated) and those injected with lacZ-encoding reporter gene HSV vectors (HSV-LacZ) were used as controls. Three weeks after viral injection, continuous cystometry was performed under awake conditions in all three groups. In the HSV-GAD group, the number and amplitude of non-voiding contractions (NVCs) were significantly decreased (40-45% and 38-40%, respectively) along with an increase in voiding efficiency, compared with HSV-untreated and HSV-LacZ groups, but micturition pressure was not different among the three groups. Intrathecal application of bicuculline partly reversed the decreased number and amplitude of NVCs, and decreased voiding efficiency in the HSV-GAD group. In the HSV-GAD group, GAD(67) mRNA and protein levels were significantly increased in the L6-S1 dorsal root ganglia (DRG) compared with the HSV-LacZ group, while 57% of DRG cells were GFP-positive, and these neurons showed increased GAD(67)-like immunoreactivity compared with the HSV-LacZ group. These results indicate that GAD gene therapy effectively suppresses DO after SCI predominantly through the activation of spinal GABA(A) receptors. Thus, HSV-based GAD gene transfer to bladder afferent pathways may represent a novel approach for treatment of neurogenic DO.

Construction and production of recombinant herpes simplex virus vectors

Virus vectors have been employed as gene transfer vehicles for various pre-clinical and clinical gene therapy applications. Replication-competent herpes simplex virus (HSV) vectors that replicate specifically in actively dividing glial tumor cells have been used in Phase I-II human trials in patients with glioblastoma multiforme (GBM), a fatal form of brain cancer. Research during the last decade on the development of HSV vectors has resulted in the engineering of recombinant vectors that are totally replication defective, non-toxic, and capable of long-term transgene expression. This chapter describes methods for the construction of recombinant genomic HSV vectors based on the HSV-1 replication-defective vector backbones, steps in their purification, and their small-scale production for use in cell culture experiments as well as studies in animals.

Herpes simplex virus vector-mediated delivery of neurturin rescues erectile dysfunction of cavernous nerve injury

Neurturin (NTN), a member of glial cell line-derived neurotrophic factor (GDNF) family, is known as an important neurotrophic factor for penis-projecting neurons. We recently demonstrated significant protection from erectile dysfunction (ED) following a replication-defective herpes simplex virus (HSV) vector-mediated GDNF delivery to the injured cavernous nerve. Herein, we applied HSV vector-mediated delivery of NTN to this ED model. Rat cavernous nerve was injured bilaterally using a clamp and dry ice. For HSV-treated groups, 20 microl of vector stock was administered directly to the damaged nerve. Delivery of an HSV vector expressing both green fluorescent protein and lacZ (HSV-LacZ) was used as a control. Intracavernous pressure along with systemic arterial pressure (ICP/AP) was measured 2 and 4 weeks after the nerve injury. Fluorogold (FG) was injected into the penile crus 7 days before being killed to assess neuronal survival. Four weeks after nerve injury, rats treated with HSV-NTN exhibited significantly higher ICP/AP compared with untreated or control vector-treated groups. The HSV-NTN group had more FG-positive major pelvic ganglion neurons than the control group following injury. HSV vector-mediated delivery of NTN could be a viable approach for the improvement of ED following cavernous nerve injury.

Construction of replication-defective herpes simplex virus vectors

Advances in identification and characterization of gene products responsible for specific diseases of the nervous system have opened opportunities for novel therapies using gene transfer vectors for gene replacement. Herpes simplex virus (HSV)-based vectors are particularly well suited for gene delivery to neurons of the central and peripheral nervous systems. The authors have developed methods to delete HSV-1 IE gene functions and to subsequently introduce foreign genes into the HSV-1 genome using homologous recombination. This unit describes methods for generating cell lines that complement multiple essential gene deletion mutants as well for generating such replication-defective virus recombinants and inserting foreign DNA sequences into replication-defective viral genomes, the last step in preparing a vector. Three support protocols describe methods for preparing virus stocks, titering virus, and preparing viral DNA.

Promoter- and cell-specific transcriptional transactivation by the Kaposi's sarcoma-associated herpesvirus ORF57/Mta protein

The Kaposi's sarcoma-associated herpesvirus (KSHV) Mta protein, encoded by open reading frame 57, is a transactivator of gene expression that is essential for productive viral replication. Previous studies have suggested both transcriptional and posttranscriptional roles for Mta, but little is known regarding Mta's transcriptional function. In this study, we demonstrate that Mta cooperates with the KSHV lytic switch protein, Rta, to reactivate KSHV from latency, but Mta has little effect on reactivation when expressed alone. We demonstrate that the Mta and Rta proteins are expressed with similar but distinct kinetics during KSHV reactivation. In single-cell analyses, Mta expression coincides tightly with progression to full viral reactivation. We demonstrate with promoter reporter assays that while Rta activates transcription in all cell lines tested, Mta's ability to transactivate promoters, either alone or synergistically with Rta, is cell and promoter specific. In particular, Mta robustly transactivates the nut-1/PAN promoter independently of Rta in 293 and Akata-31 cells. Using nuclear run-on assays, we demonstrate that Mta stimulates transcriptional initiation in 293 cells. Rta and Mta physically interact in infected cell extracts, and this interaction requires the intact leucine repeat and central region of Rta in vitro. We demonstrate that Mta also binds to the nut-1/PAN promoter DNA in vitro and in infected cells. An Mta mutant with a lesion in a putative A/T hook domain is altered in DNA binding and debilitated in transactivation. We propose that one molecular mechanism of Mta-mediated transactivation is a direct effect on transcription by direct and indirect promoter association.

Relaxed repression of herpes simplex virus type 1 genomes in Murine trigeminal neurons

The expression of herpes simplex virus (HSV) genomes in the absence of viral regulatory proteins in sensory neurons is poorly understood. Previously, our group reported an HSV immediate early (IE) mutant (d109) unable to express any of the five IE genes and encoding a model human cytomegalovirus immediate early promoter-green fluorescent protein (GFP) transgene. In cultured cells, GFP expressed from this mutant was observed in only a subset of infected cells. The subset exhibited cell type dependence, as the fractions of GFP-expressing cells varied widely among the cell types examined. Herein, we characterize this mutant in murine embryonic trigeminal ganglion (TG) cultures. We found that d109 was nontoxic to neural cultures and persisted in the cultures throughout their life spans. Unlike with some of the cultured cell lines and strains, expression of the GFP transgene was observed in a surprisingly large subset of neurons. However, very few nonneuronal cells expressed GFP. The abilities of ICP0 and an inhibitor of histone deacetylase, trichostatin A (TSA), to activate GFP expression from nonexpressing cells were also compared. The provision of ICP0 by infection with d105 reactivated quiescent genomes in nearly every cell, whereas reactivation by TSA was much more limited and restricted to the previously nonexpressing neurons. Moreover, we found that d109, which does not express ICP0, consistently reactivated HSV type 1 (KOS) in latently infected adult TG cultures. These results suggest that the state of persisting HSV genomes in some TG neurons may be more dynamic and more easily activated than has been observed with nonneuronal cells.

DNA-dependent oligomerization of herpes simplex virus type 1 regulatory protein ICP4

The human herpes simplex virus type 1 regulatory protein ICP4 binds DNA as a dimer and forms a single protein-DNA complex (A complex) with short DNA probes. ICP4 oligomerized in a DNA-dependent manner, forming two or more protein-DNA complexes with longer DNA fragments containing a single DNA binding site. When resolved electrophoretically, one or more low-mobility DNA-protein complexes follow the fast-moving A complex. The major protein-DNA complex (B complex) formed by ICP4 with long DNA probes migrates just behind the A complex in the electric field, implying the oligomerization of ICP4 on the DNA. Binding experiments with circularly permutated DNA probes containing one ICP4 binding site revealed that about 70 bp of nonspecific DNA downstream of the cognate ICP4 binding site was required for efficient B complex formation. In addition, the C-terminal domain of ICP4 was found to be required for DNA-dependent oligomerization and B complex formation. Gel mobility shift analysis of protein-DNA complexes, combined with supershift analysis using different monoclonal antibodies, indicated that the B complex contained two ICP4 dimers. DNase I footprinting of ICP4-DNA complexes showed that one ICP4 dimer contacts the specific binding site and another ICP4 dimer contacts nonspecific DNA in the B complex. DNA-dependent oligomerization increased the affinity of ICP4 for relatively weak binding sites on large DNA molecules. The results of this study suggest how ICP4 may use multiple weak binding sites to aid in transcription activation.

Herpes simplex virus vector-mediated delivery of glial cell line-derived neurotrophic factor rescues erectile dysfunction following cavernous nerve injury

Erectile dysfunction (ED) is frequently associated with injury to the cavernous nerve sustained during pelvic surgery. Functional recovery from cavernous nerve injury is generally incomplete and occurs over an extended time frame. We employed a therapeutic gene transfer approach with herpes simplex virus (HSV) vector expressing glial cell line-derived neurotrophic factor (GDNF). Rat cavernous nerve was injured bilaterally using a clamp and dry ice. For HSV-treated groups, 20 microl of purified vector stock was administered directly to and around the damaged nerve. Delivery of an HSV vector expressing both green fluorescent protein (GFP) and lacZ (HSV-LacZ) was used as a control. Intracavernous pressure along with systemic arterial pressure (ICP/AP) was measured 2 and 4 weeks after the nerve injury. Fluorogold (FG) was injected into the penile crus 7 days before killing to assess nerve survival. Approximately 60% of major pelvic ganglion (MPG) cells were GFP positive after viral administration. At 4 weeks after nerve injury, rats treated with HSV-GDNF exhibited significant recovery of ICP/AP compared with control vector or untreated groups. The HSV-GDNF group also yielded more FG-positive MPG cells than the control vector group. HSV vector-mediated delivery of GDNF presents a viable approach for the treatment of ED following cavernous nerve injury.

Resveratrol suppresses nuclear factor-kappaB in herpes simplex virus infected cells

Resveratrol inhibits herpes simplex virus (HSV) replication by an unknown mechanism. Previously it was suggested that this inhibition may be mediated through a cellular factor essential for HSV replication [Docherty, J.J., Fu, M.M., Stiffler, B.S., Limperos, R.J., Pokabla, C.M., DeLucia, A.L., 1999. Resveratrol inhibition of herpes simplex virus replication. Antivir. Res. 43, 145-155]. After examining numerous cellular factors, we report that resveratrol suppresses NF-kappaB (NF-kappaB) activation in HSV infected cells. Reports have indicated that HSV activates NF-kappaB during productive infection and this may be an essential aspect of its replication scheme [Patel, A., Hanson, J., McLean, T.I., Olgiate, J., Hilton, M., Miller, W.E., Bachenheimer, S.L., 1998. Herpes simplex type 1 induction of persistent NF-kappa B nuclear translocation increases the efficiency of virus replication. Virology 247, 212-222; Gregory, D., Hargett, D., Holmes, D., Money, E., Bachenheimer, S.L., 2004. Efficient replication by herpes simplex virus type 1 involves activation of the IkappaB kinase-IkappaB-RelA/p65 pathway. J. Virol. 78, 13582-13590]. Electromobility shift assays determined that resveratrol, in a dose dependent and reversible manner, suppressed activation of NF-kappaB in Vero cells infected with HSV-1, HSV-2 and acyclovir resistant HSV-1. Furthermore, resveratrol did not protect IkappaBalpha, a cytoplasmic NF-kappaB inhibitor, from degradation in HSV-1 infected cells. Immunohistochemical studies demonstrated that RelA/p65, a component of the dimeric NF-kappaB complex, translocated to the nucleus of HSV-1 infected cells in the presence of resveratrol. Finally, direct effects on viral transcription and DNA synthesis were evaluated. Real-time RT-PCR analysis showed that resveratrol treatment of infected cells resulted in reductions of mRNA for ICP0, ICP4, ICP8 and HSV-1 DNA polymerase by 2.1-, 3.3-, 3.8- and 3.1-fold, respectively. Plus, mRNA for glycoprotein C, an HSV late gene, was completely absent in the presence of resveratrol. Lastly, quantitative PCR showed that resveratrol significantly blocked HSV DNA synthesis. Cumulatively, these data indicate that resveratrol (i) suppresses HSV induced activation of NF-kappaB within the nucleus and (ii) impairs expression of essential immediate-early, early and late HSV genes and synthesis of viral DNA.

Degradation of fibrillar collagen in a human melanoma xenograft improves the efficacy of an oncolytic herpes simplex virus vector

Oncolytic viral therapy provides a promising approach to treat certain human malignancies. These vectors improve on replication-deficient vectors by increasing the viral load within tumors through preferential viral replication within tumor cells. However, the inability to efficiently propagate throughout the entire tumor and infect cells distant from the injection site has limited the capacity of oncolytic viruses to achieve consistent therapeutic responses. Here we show that the spread of the oncolytic herpes simplex virus (HSV) vector MGH2 within the human melanoma Mu89 is limited by the fibrillar collagen in the extracellular matrix. This limitation seems to be size specific as nanoparticles of equivalent size to the virus distribute within tumors to the same extent whereas smaller particles distribute more widely. Due to limited viral penetration, tumor cells in inaccessible regions continue to grow, remaining out of the range of viral infection, and tumor eradication cannot be achieved. Matrix modification with bacterial collagenase coinjection results in a significant improvement in the initial range of viral distribution within the tumor. This results in an extended range of infected tumor cells and improved virus propagation, ultimately leading to enhanced therapeutic outcome. Thus, fibrillar collagen can be a formidable barrier to viral distribution and matrix-modifying treatments can significantly enhance the therapeutic response.

UL54-null pseudorabies virus is attenuated in mice but productively infects cells in culture

The pseudorabies virus (PRV) UL54 homologs are important multifunctional proteins with roles in shutoff of host protein synthesis, transactivation of virus and cellular genes, and regulation of splicing and translation. Here we describe the first genetic characterization of UL54. We constructed UL54 null mutations in a PRV bacterial artificial chromosome using sugar suicide and lambdaRed allele exchange systems. Surprisingly, UL54 is dispensable for growth in tissue culture but exhibits a small-plaque phenotype that can be complemented in trans by both the herpes simplex virus type 1 ICP27 and varicella-zoster virus open reading frame 4 proteins. Deletion of UL54 in the virus vJSdelta54 had no effect on the ability of the virus to shut off host cell protein synthesis but did affect virus gene expression. The glycoprotein gC accumulated to lower levels in cells infected with vJSdelta54 compared to those infected with wild-type virus, while gK levels were undetectable. Other late gene products, gB, gE, and Us9, accumulated to higher levels than those seen in cells infected with wild-type virus in a multiplicity-dependent manner. DNA replication is also reduced in cells infected with vJSdelta54. UL54 appears to regulate UL53 and UL52 at the transcriptional level as their respective RNAs are decreased in cells infected with vJSdelta54. Interestingly, vJSdelta54 is highly attenuated in a mouse model of PRV infection. Animals infected with vJSdelta54 survive twice as long as animals infected with wild-type virus, and this results in delayed accumulation of virus-specific antigens in skin, dorsal root ganglia, and spinal cord tissues.

Mapping of functional regions conferring nuclear localization and RNA-binding activity of pseudorabies virus early protein UL54

Pseudorabies virus (PRV) is an alphaherpesvirus, and its gene organization and regulation are similar to the well-characterized human herpes simplex virus (HSV). The PRV early protein UL54 consists of 363 amino acids with homology to the HSV ICP27 immediate-early protein. Previously, we have demonstrated the nuclear accumulation and poly(G) RNA-binding activity of UL54 protein. In the present study, we have identified further the functional regions within UL54 conferring for nuclear localization and RNA-binding activity. Several recombinant expression plasmids containing various coding regions of UL54 gene were constructed for producing a series of C-terminally truncated or internally deleted forms of UL54 mutants in Escherichia coli or porcine kidney (PK-15) cells. RNA-binding activity of E. coli-expressed UL54 mutants was characterized by the binding ability to poly(G) RNA homopolymer in dot blot hybridization assay and the results have shown that the N-terminal 83 residues were responsible for RNA-binding, and the region of residues 35-82 containing an RGG box was necessary for its function. Furthermore, the region responsible for nuclear localization was investigated by transient expression of various deletion mutants in PK-15 cells followed by detection of their subcellular distribution. The results showed that C-terminal deletion beyond the amino acid residue 83 or internal deletion containing the RGG box sequence could restrict UL54 mutants in the cytoplasm. The ability of the N-terminal 83 residues to target the green fluorescence protein to the nucleus confirmed further its role as a functional nuclear localization signal (NLS). The utmost N-terminal 83 residues portion of UL54 contains two important functional domains, NLS and RNA-binding, and thus it would play an indispensable role in UL54 regulatory function.

Evidence for a direct interaction between HSV-1 ICP27 and ICP8 proteins

Herpes simplex virus 1 (HSV-1) ICP27 and ICP8 proteins have both been implicated in the transcription of late genes and regulation of viral gene expression. We showed previously that ICP27 and ICP8 associate with the RNAP II holoenzyme (Zhou and Knipe, J. Virol. 76, 5893-5904). Here, we demonstrate that ICP27 and ICP8 coprecipitate from lysates of HSV-1-infected HEp2 cells and from lysates of insect cells expressing ICP27 and ICP8, the latter being in the absence of other HSV-1 proteins. By expressing and purifying hexahistidine-tagged ICP8 (His-ICP8) and maltose binding protein (MBP)-tagged ICP27 (MBP-27) proteins and performing in vitro immunoprecipitation and pull-down assays, we also demonstrate that ICP27 and ICP8 coprecipitate in the absence of other viral or cellular proteins. Taken together, these data provide evidence that ICP27 and ICP8 interact directly in vitro and in infected cells. We hypothesize that the ICP27-ICP8 interaction plays a role in the stimulation of late gene transcription.

Safety and biodistribution studies of an HSV multigene vector following intracranial delivery to non-human primates

Malignant glioma is a fatal human cancer in which surgery, chemo- and radiation therapies are ineffective. Therapeutic gene transfer used in combination with current treatment methods may augment their effectiveness with improved clinical outcome. We have shown that NUREL-C2, a replication-defective multigene HSV-based vector, is effective in treating animal models of glioma. Here, we report safety and biodistribution studies of NUREL-C2 using rhesus macaques as a model host. Increasing total doses (1 x 10(7) to 1 x 10(9) plaque forming units (PFU)) of NUREL-C2 were delivered into the cortex with concomitant delivery of ganciclovir (GCV). The animals were evaluated for changes in behavior, alterations in blood cell counts and chemistry. The results showed that animal behavior was generally unchanged, although the chronic intermediate dose animal became slightly ataxic on day 12 postinjection, a condition resolved by treatment with aspirin. The blood chemistries were unremarkable for all doses. At 4 days following vector injections, magnetic resonance imaging showed inflammatory changes at sites of vector injections concomitant with HSV-TK and TNFalpha expression. The inflammatory response was reduced at 14 days, resolving by 1 month postinjection, a time point when transgene expression also became undetectable. Immunohistochemical staining following animal killing showed the presence of a diffuse low-grade gliosis with infiltrating macrophages localized to the injection site, which also resolved by 1 month postinoculation. Viral antigens were not detected and injected animals did not develop HSV-neutralizing antibodies. Biodistribution studies revealed that vector genomes remained at the site of injection and were not detected in other tissues including contralateral brain. We concluded that intracranial delivery of 1 x 10(9) PFU NUREL-C2, the highest anticipated patient dose, was well tolerated and should be suitable for safety testing in humans.

Characterization and expression of the pseudorabies virus early gene UL54

Pseudorabies virus (PRV) is an alphaherpesvirus, and its gene organization and regulation are similar to the well-characterized human simplex virus (HSV). Sequence analysis of the complete coding region of PRV UL54 gene revealed that the UL54 gene consisted of 1092 nucleotides encoding a protein of 363 amino acids and the gene showed homology to HSV immediate-early protein ICP27. Detection of the UL54 transcript in infected cells by reverse transcription-polymerase chain reaction (RT-PCR) demonstrated that the UL54 gene belonged to the early kinetic class based on sensitivity to cycloheximide and insensitivity to phosphonoacetic acid (PAA). To study the structure and function of UL54 protein, this gene was subcloned on Escherichia coli expression vector pET28b for overexpression, and the expressed product was applied to generate specific antibody against UL54 protein. The specificity of the mouse immuneserum was confirmed by its ability to react with a 40kDa viral protein present in the PRV infected cells in Western immunblotting assay, detected as early as 4h after infection. In addition, immunoperoxidasing staining of PRV infected cells undertaken with this antibody demonstrated mainly nuclear staining pattern. Furthermore, the RNA binding potential of UL54 protein was demonstrated by its binding activity to poly(G) RNA homopolymer in Northwestern blotting assay.

Herpes simplex virus 1 infection is required to produce ICP27 immunoreactive triplet forms when ribosomal aminoacyl-tRNA translocation is blocked by cycloheximide

Infected cell protein (ICP) 27 is an essential herpes simplex virus type 1 (HSV-1) phosphoprotein required for optimal viral DNA and early or late gene synthesis. Three slow-migrating immunoreactive species were detected using multiple anti-ICP27 antibodies following HSV-1 infection of HEp-2 and Vero cells in the presence of cycloheximide (CHX). Generation of the protein triplet moieties required transcription of the alpha27 gene. These forms were observed following infection with a series of recombinant viruses that produce truncated ICP27 polypeptides, suggesting that alternative splicing is not involved in the process. These ICP27 species were not observed following translation inhibition by puromycin (PUR). Synthesis of the triplet occurred by 6 hpi and CHX addition as late as 3 hpi still enabled their production. That the ICP27 species were detected in uninfected ICP27-expressing cells without CHX, but not in its presence, suggests a mechanism in which virus infection is required to produce the forms when ribosomal aminoacyl-transfer RNA (tRNA) translocation is blocked.

Transactivation of a viral target gene by herpes simplex virus ICP27 is posttranscriptional and does not require the endogenous promoter or polyadenylation site

ICP27 is an essential herpes simplex virus type 1 (HSV-1) immediate-early protein that stimulates viral mRNA expression from many viral delayed-early and late genes during infection. One HSV-1 late gene which is highly dependent on ICP27 during infection is that encoding the glycoprotein C (gC). Here we report that the gC gene is specifically transactivated by ICP27 in transfected Vero cells. Using various gC plasmid constructs, we show that ICP27's stimulatory effects are independent of the gC gene's endogenous promoter and polyadenylation site. This suggests that ICP27-responsive elements lie in the transcribed body of the gC gene. We also show that transactivation of the gC gene by ICP27 is independent of other viral proteins, as ICP27 alone can transactivate the gC gene when its transcription is mediated by the human cytomegalovirus immediate-early gene promoter. However, when gC gene expression is driven by its endogenous promoter, the stimulatory effect of ICP27 requires additional transactivators. To explore the level at which ICP27 transactivates the gC gene, we established stably transfected Vero cell lines that have integrated copies of the gC gene under control of the cytomegalovirus immediate-early gene promoter. These gC genes are not constitutively expressed but can be efficiently induced by HSV-1 infection. Using nuclear run-on transcription assays, we show that transcriptional induction of the stably transfected genes is ICP27 independent. In contrast, accumulation of gC mRNA is very highly dependent on ICP27. Together, these results demonstrate that ICP27 posttranscriptionally activates mRNA expression from a biologically relevant viral target gene.

Viral oncoapoptosis of human tumor cells

Many cancer cells refractory to radiation treatment and chemotherapy proliferate because of loss of intrinsic programmed cell death (apoptosis) regulation. Consequently, the resolution of these cancers are many times outside the management capabilities of conventional therapeutics. We now report that replication-defective delta27 herpes simplex virus (rd delta27) triggers apoptosis in three representative transformed human cell lines. Susceptibility to virus-induced cell death is dependent on the abundance and distribution of modified p53 protein in the tumor cells indicating specific targeting of the treatment. Primary human and mouse fibroblast cells that produce modified p53 are resistant to rd delta27 killing but not to apoptosis induced by nonviral environmental factors. These results suggest that induction of apoptosis by nonreplicating virus is a feasible genetic therapy approach for killing human cancer cells. Our findings may have important implications in designing novel virus-based anticancer strategies in appropriate animal model systems.

Relationship of herpes simplex virus genome configuration to productive and persistent infections

Infection of susceptible cells by herpes simplex virus (HSV) can lead to productive infection or to latency, where the genomes persist in the nuclei of peripheral neurons in a quiescent state. Using the HSV strain d109, which does not express any viral genes and thus establishes a quiescent state in most cells, we observed that a fraction of genomes circularized upon infection. The expression of infected cell protein (ICP) 0, which is known to be involved in reactivation from latency and the promotion of productive infection, inhibited the formation of circular genomes. Circular genomes were not observed upon infection of fully permissive cells by wild-type virus, in either the presence or absence of viral DNA replication. However, productive infection in the absence of ICP0 resulted in the accumulation of a subpopulation of circular genomes. The proportion of circular genomes formed during infection with an ICP0 mutant was greater at low multiplicity of infection, a condition in which ICP0 mutants replicate poorly. In the complete absence of viral gene expression, it was found that only circular genomes persisted in cells. These results suggest that circularization of the HSV genome may not occur early in the productive phase of wild-type HSV infection, but rather during establishment of a quiescent state or latency, providing a possible strategy for long-term persistence. Additionally, the circularization and possible fate of HSV genomes are regulated by an activity of ICP0.

Gene delivery using herpes simplex virus vectors

Herpes simplex virus (HSV) is a neurotropic DNA virus with many favorable properties as a gene delivery vector. HSV is highly infectious, so HSV vectors are efficient vehicles for the delivery of exogenous genetic material to cells. Viral replication is readily disrupted by null mutations in immediate early genes that in vitro can be complemented in trans, enabling straightforward production of high-titre pure preparations of non-pathogenic vector. The genome is large (152 Kb) and many of the viral genes are dispensable for replication in vitro, allowing their replacement with large or multiple transgenes. Latent infection with wild-type virus results in episomal viral persistence in sensory neuronal nuclei for the duration of the host lifetime. Transduction with replication-defective vectors causes a latent-like infection in both neural and non-neural tissue; the vectors are non-pathogenic, unable to reactivate and persist long-term. The latency active promoter complex can be exploited in vector design to achieve long-term stable transgene expression in the nervous system. HSV vectors transduce a broad range of tissues because of the wide expression pattern of the cellular receptors recognized by the virus. Increasing understanding of the processes involved in cellular entry has allowed preliminary steps to be taken towards targeting the tropism of HSV vectors. Using replication-defective HSV vectors, highly encouraging results have emerged from recent pre-clinical studies on models of neurological disease, including glioma, peripheral neuropathy, chronic pain and neurodegeneration. Consequently, HSV vectors encoding appropriate transgenes to tackle these pathogenic processes are poised to enter clinical trials.

The Epstein-Barr virus SM protein is functionally similar to ICP27 from herpes simplex virus in viral infections

The herpes simplex virus type 1 (HSV-1) ICP27 protein is an essential RNA-binding protein that shuttles between the nucleus and cytoplasm to increase the cytoplasmic accumulation of viral late mRNAs. ICP27 homologs have been identified in each of the herpesvirus subfamilies, and accumulating evidence indicates that homologs from the gammaherpesvirus subfamily function similarly to ICP27. In particular, the Epstein-Barr virus (EBV) SM protein posttranscriptionally regulates gene expression, binds RNA in vitro and in vivo, and shuttles between the nucleus and cytoplasm. To determine if these two proteins function through a common mechanism, the ability of EBV SM to complement the growth defect of an HSV-1 ICP27-null virus was examined in a transient-expression assay. ICP27 stimulated the growth of the null mutant more efficiently than did SM, but the ability of SM to compensate for the ICP27 defects suggests conservation of common functions. To assay for complementation in the context of a viral infection, the growth properties of an HSV recombinant expressing SM in an ICP27-null background were analyzed. SM stimulated growth of the recombinant, although this growth was reduced by comparison to that of an ICP27-expressing virus. By contrast, an HSV recombinant expressing an SM mutant allele defective for transactivation activity and nucleocytoplasmic shuttling did not grow at all. These results suggest that SM and ICP27 may regulate gene expression through a common pathway that is evolutionarily conserved in herpesviruses.